While the FBI-led investigation into last Monday’s deadly bombing that killed three and wounded more than 260 remains in its early stages, the Arizona Republican said on Tuesday it is too soon to dismiss the Tsarnaev brothers’ possible links to the Islamic extremist group.

“The Boston attacks were clearly inspired by the violent ideology of transnational Islamist terrorism,” McCain said on the Senate floor. “So we need to learn everything we can about what foreign terrorists or terrorist groups the suspect and his brother might have associated with — whether they were part of additional plots to attack our nation — and what other relevant information the suspect may possess that could prevent future attacks against the United States or our interests.”

The White House announced Monday that Dzhokhar Tsarnaev would be tried in federal criminal court, and criminal charges have been filed. Lying in his hospital bed recovering from serious wounds sustained during two shootouts with law enforcement officers, the surviving bombing suspect was also read his Miranda Rights.

That appeared to shift the Boston bombing away from the national security sphere and into the criminal realm.

But then McCain and Sen. Lindsey Graham, R-S.C., who made the first congressional call for American citizen Tsarnaev to be held and questioned as an enemy combatant without receiving a Miranda reading, took to the Senate floor.

“The administration gave up a valuable opportunity to lawfully and thoroughly question the suspect for purposes of gathering intelligence about potential future terrorist plots,” McCain said. “Whether we will be able to acquire such information has now been left entirely at the discretion of the suspect and his lawyer. Put simply, the suspect has been told he has the right to remain silent; and, if he doesn’t want to provide intelligence, he doesn’t have to.”

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The two Senate Armed Services Committee members are attempting to keep the matter in the national security sphere, setting up a potential fight when the committee begins finalizing its version of the fiscal 2014 defense authorization bill in a few months.

Panel Chairman Sen. Carl Levin, D-Mich., said in a statement issued Saturday that he is unaware of any legal basis under which the younger Tsarnaev could be held and interrogated as an enemy combatant.

“I am not aware of any legal basis at this point for such a designation in this case. Under the law of war, we have the authority to detain individuals who join a hostile foreign force engaged in attacking the United States,” Levin said. “The 2001 Authorization for Use of Military Force authorizes such detention in the case of an individual who is a part of al-Qaida, the Taliban, or an associated force.

"I am not aware of any evidence so far that the Boston suspect is part of any organized group, let alone al-Qaida, the Taliban, or one of their affiliates,” Levin said. “In the absence of such evidence I know of no legal basis for his detention as an enemy combatant. To hold the suspect as an enemy combatant under these circumstances would be contrary to our laws and may even jeopardize our efforts to prosecute him for his crimes.”

But McCain and Graham say that since Tsarnaev was unable to communicate for several days and still is unable to talk to investigators, it’s too soon to say whether the alleged bombers were members of or working with al-Qaida.

“The full extent of whether the suspect is linked to al-Qaida or its associated forces remains unclear. The [older, dead] brother’s trip to Russia should certainly be the subject of an inquiry,” McCain said. “And additional questioning is critical to making that clear. But today there is ample evidence that would allow the administration to question the suspect for key intelligence.

“The consequence of not doing so is that our need to question this suspect for such intelligence is left solely at his discretion and willingness to cooperate. That is not a responsible approach to the national security of this country.

McCain and Graham believe Washington has the legal right to hold an American citizen who was apprehended in the United States for an action conducted there as an enemy combatant because they see the “homeland as part of the battlefield” in the congressionally approved war against al-Qaida.